Incrementing a number in qt c++

In my code I need to increment an integer used by 2 methods(button clicks)! 1 method is used to display the integer(starting value is 1) in a line edit when a button is clicked! The other button is used to increment the number! I need to declare the integer in the header file to be used by the two methods! But in the header file we can declare only static constant so when I increment the error I get an error! How can I avoid this?